Disc brakes are commonly used for braking heavy vehicles such as trucks, buses and coaches.
Disc brakes conventionally comprise a brake carrier, a caliper and a rotor. The carrier is arranged to carry brake pads on each side of the rotor. The caliper is slidably mounted on the brake carrier by two or more guide assemblies, such that when the disc brake is actuated, the caliper is able to slide with respect to the brake carrier. As the caliper slides inboard, the brake pads are urged onto the opposing faces of the rotor in a clamping action and a braking action is effected.
A guide assembly typically comprises a guide pin along which the caliper can slide and a bore disposed in the caliper for receiving the guide pin. Typically each guide pin comprises a smooth outer guide sleeve along which the caliper slides and a guide bolt which extends through the guide sleeve and is screwed into a bore of the brake carrier to retain the guide sleeve.
This arrangement has been proven over many years of usage. However, it has been recognized that in certain testing conditions, specifically when a vehicle undergoes a significant number of forward and reverse movements, there is a risk that the guide bolt of the disc brake may rotate and loosen.
Previous attempts to solve this problem have utilized lock patches to inhibit rotation of the guide bolt.
However, the present inventors have recognized that this approach in effect deals with a symptom of the problem rather than the cause. The present inventors have also identified that the cause of the loosening bolt problem is the rotation of the guide sleeve and the rotation of the guide sleeve being frictionally transmitted into rotation of the bolt.
The present invention seeks to overcome or at least mitigate the problems of the prior art.